I made 14 new rooms for the game. They should all be fair and fit within normal gameplay. The developers can include these rooms in the game officially, if they want.
Usage instructions: extract the .zip file in the Skyward Rogue folder, and combine the folders. The levels will now appear randomly in the game.
You can also try them out individually. Open Starward Rogue\RuntimeData\Configuration\TestChambers\a_testReathRooms.xml in a text editor. Start the game, then pick the mods options in the file selection window. Select a_TestReathRooms in the Test Chamber dropdown. The first level will now load. To change levels, alt tab to the text editor, then copy and paste one of the room_setup scripts on top of the one at the top. Return to the game, press esc and select reload test chamber. The new room will then load.
To remove the new rooms, delete all files with the Reath_ prefix in the Starward Rogue\RuntimeData\Rooms directories.